Genetic relationship between Neck and Limb defects in Pura Raza Española Horses

Abstract

Background: Neck and limb conformational defects can impair functionality and performance in Pura Raza Española (PRE) horses. However, their potential genetic relationship has not been previously explored. Aims/objectives: To estimate the genetic correlations between two types of neck defects (Cresty neck -CN-, Ewe neck -EN-) and twelve conformational limb defects: Forelimb (Buck knee -BUK-, Calf knee -CK-, Bench knee -BEK-, Knock knee -KK-, Splay-footed forelimb -SFF-, Pigeon-toed forelimb -PTF-), rear limb (Closed hock -CH-, Open hock -OH-, Convergent hock -CVH-, Divergent hock -DVH-, Splay-footed rear limb -SFR-, Pigeon-toed rear limb -PTR-). We hypothesized that a genetic relationship exists between neck and limb morphology. Methods: This study analyzed 56,644 PRE horses evaluated between 2012 and 2023. Neck and limb conformation traits were scored using two approaches: A) two-class scale (0-no defect, 1-presence of defect); B) three-class scale for limb defects (0-no defect, 1-slight defect, 2-serious defect) and four-class scale for neck defects (0-no defect, 1-slight defect, 2-serious defect, 3-disqualifying defect). Genetic parameters were estimated, including age as a covariate, and sex, genetic origin, management of breeder's stud farm and inbreeding as fixed effects. Results: The most frequent limb defect among horses with neck defects was SFR (80.15 % in CN and 72.45 % in EN). Genetic correlations showed moderate relationships, ranging from -0.22(s.d.: 0.090) for EN-SFR to 0.44(s.d.: 0.123) for CN-DVH in approach A, and oscillating from -0.25(s.d.: 0.028) for CNCVH to 0.51(s.d.: 0.228) for CN-SFF in approach B. Conclusion: Results support the need for integrated selection strategies targeting both anatomical region